Pressure pin capturing system for traveling bolsters

ABSTRACT

Apparatus for carrying and releasing pressure pins associated with drawing dies mounted on traveling bolsters for presses, such bolsters being mounted for movement between loading positions spaced from the press ram area and working positions in alignment beneath the ram. The present apparatus includes a plate mounted in the bolster which moves generally transverse to the direction of motion of the pins and opposite to the direction of motion of the bolster for releasing the pins for reciprocal movement when the bolster is in the working position. Camming means are included for each pin in one embodiment, the camming means having an eccentric camming surface for alternately capturing and releasing the pins.

United States Patent [1 1 Smit 4 1 Jan. 28, 1975 [75] Inventor: Henry Smit, Kentwood, Mich.

[73] Assignee: Leslie E. Tassell, Grand Rapids,

Mich. a part interest [22] Filed: Sept. 10, 1973 [21] Appl. No.: 396,011

Related US. Application Data [63] Continuation-in-part of Ser. No. 263,147, June 15,

1972, Pat. N0. 3,818,748.

[52] US. Cl 72/448, 83/400, 100/229, IOO/DIG. 18 [51] int. Cl B2lj 13/00 [58] Field of Search 72/446, 448, 419; 100/229, 100/46, 214, DIG. 18; 83/400; 29/568 3,446,106 3/1969 Ferris 83/400 3,498,102 3/1970 Warstler.. 72/470 3,777,602 12/1973 Youra 1. 83/400 Primary Examiner-C. W. Lanham Assistant Exuminer-Gene P. Crosby Attorney, Agent, or Firm-Price, Heneveld, Huizenga & Cooper [57] V ABSTRACT Apparatus for carrying and releasing pressure pins associated with drawing dies mounted on traveling bolsters for presses, such bolsters being mounted for movement between loading positions spaced from the press ram area and working positions in alignment beneath the ram. The present apparatus includes a plate mounted in the bolster which moves generally transverse to the direction of motion of the pins and opposite to the direction of motion of the bolster for releasing the pins for reciprocal movement when the bolster is in the working position. Camming means are included for each pin in one embodiment, the cumming means having an eccentric camming surface for alternately capturing and releasing the pins.

22 Claims, 9 Drawing Figures PATENTEI] JANZ 8 I975 sum NF 5 FIG. 9

PRESSURE PIN CAPTURING SYSTEM FOR TRAVELING BOLSTERS This application is a continuation-in-part of the prior pending application Ser. No. 263,147, entitled SAFETY APPARATUS FOR PRESSES, invented by Henry Smit, filed June 15, 1972, now US. Pat. No. 3,818,748, which application is specifically incorporated by reference herein.

The present invention relates to pressure pin mounting systems for inclusion on traveling bolsters for presses, and, more particularly, to a means for capturing and releasing at desired times the pressure pin utilized in conjunction with drawing dies on traveling bolsters for power presses.

BACKGROUND OF THE INVENTION Traveling bolsters for presses which move between a loading position spaced away from the ram area of a press and a working position in alignment beneath the ram are conventionally known. One such traveling bolster which may be incorporated for safety reasons on a power press to prevent injury to the operator of the press is shown and described in application Ser. No. 263,147 mentioned above, which application is the parent of the present application. Such traveling bolster assemblies have revolutionized the press industry and have completely eliminated the operators fear of the press machinery since the operators hands and arms are'precluded from being caught in the ram area .when the press is in operation. The result has been an increase in productivity with presses utilizing such assemblies accompanied by elimination of operator injury.

In certain operations with presses, it is necessary to utilize drawing dies wherein pressure pins are mounted in the assembly below the press ram such that the pins cooperate with the ram of the press to capture and retain a piece of material to be worked prior to its being drawn over or formed about a portion of the lower drawing die or draw post. Such pressure pins are commonly known and are usually associated with a pressure pin bumper or buffer means, such as an air cushion pad beneath the press bed, which damps and resists the movement of the pressure pins whereby the material to be worked is properly clamped during the ram operation. A drawing ring is normally mounted on the end of the pressure pins with the material to be worked placed on the drawing ring and thereafter clamped between the ram and the ring as it is drawn over the lower die.

The incorporation of traveling bolsters in presses of the type mentioned above makes it impossible to utilize pressure pins mounted in the conventional manner. Such pins remain in a fixed position with respect to the buffer or cushion means and extend through the normal location of a stationary bolster plate and would accordingly prevent the movement of the traveling bolster plate.

Attempts have been made with prior apparatuses to overcome the above problem by including pressure pins which move in unison with the traveling bolster assemblies. Such attempts are shown, for example, in US. Pat. Nos. 3,111,100 to Georgeff issued Nov. 19, 1963, and entitled QUICK DIE CHANGE PRESS, and 3,371,515 to Munschauer, Jr. issued Mar. 5, 1968, and entitled DIE LOADING APPARATUS FOR POWER PRESSES. Both of these patents disclose apparatuses which limit the downward movement of the pressure pins. in order to utilize such designs, it is necessary to provide bulkly spacing means which space the drawing die and material to be worked a great distance above the traveling bolster and to provide a large area within the bolster in order to allow the pins to move downwardly a sufficient distance during the drawing opera tion. Accordingly, such apparatuses are undesirable, especially in smaller presses where space is very limited and wherein a drawing die cannot be spaced a large distance above the plane on which the traveling bolster moves. The present apparatus obviates the problems and provides a simple, highly efficient, space-saving, pin capturing and releasing system which does not limit the downward movement of the pressure pins.

SUMMARY OF THE INVENTION Therefore, it is the purpose of the present invention to provide a pressure pin capturing and releasing apparatus for use in conjunction with traveling bolsters for power presses which is highly efficient in operation, requires minimal space in the bolster assembly, and which does not limit movement of the pressure pins. With this invention, the pressure pins may be reciprocated against the opposing force of the buffer or cushion to a level flush with the top surface of the traveling bolster without being impeded by any part of the capturing and releasing structure. Individual pressure pins may be selectively placed in any of a plurality of pinreceiving apertures spaced around the expanse of the bolster plate. This provides necessary versatality for accommodating various size drawing dies and the like. When the pins are placed in the receiving holes, the present capturing and releasing system carries and restrains the pins during all movement of the traveling bolster between its loading and working positions, but releases the pins and allows them to reciprocate under the action of the ram forcing them against the buffer or cushion in the press bed when the bolster is in the working position.

Two embodiments of the capturing and releasing apparatus are disclosed herein, both including a plate member slidably disposed in a recess formed in the bot? tom of the traveling bolster. The plate member is slidably movable generally in a direction parallel to the top surface of the bolster. The pin-receiving holes extend downwardly through the bolster generally perpendicular to the top surface thereof. A like number of holes are provided in the sliding plate member. Means are provided for sliding the plate member in a direction opposite to the direction of movement of the traveling bolster such that as the bolster reaches its working position, the sliding plate is held against further movement while the bolster continues to its aligned position with the press ram thereby bringing the pin-receiving apertures in the bolster and plate member into registry and allowing the pins to be reciprocated under the force of the press ram.

In the first embodiment, a camming plate is provided adjacent each pin aperture in the sliding plate. The camming plate includes an eccentric camming surface which engages a shoulder on one of the pins to alternately capture and release the pin.

in a second embodiment, the sliding plate received in the traveling bolster includes an elongated slot which is moved under a larger diameter portion of the pin to BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary, perspective view of a press incorporating a traveling bolster and one embodiment of the pressure pin capturing and releasing system;

FIG. 2 is a sectional view through the traveling bolster and press bed taken along plane II-Il of FIG. 1;

FIG. 3 is a fragmentary, plan view of a portion of the traveling bolster shown in FIGS. 1 and 2 with portions of the bolster broken away, the right half of the figure illustrating the apparatus when the pressure pins are released while the left half illustrates the apparatus when the pins are captured;

FIG. 4 is a front elevation of the assembly shown in FIG. 3;

FIG. 5 is a plan view of the camming plate used in the first embodiment of the present invention;

FIG. 6 is a front elevation of the camming plate shown in FIG. 5;

FIG. 7 is an enlarged, fragmentary, sectional view of area VII shown in FIG. 2;

FIG. 8 is a fragmentary, plan view of a traveling bolster including a second embodiment of the present invention, the right half of the figure illustrating the apparatus in the position when the pins are released while the left half of the figure illustrates the apparatus when the pins are captured; and

FIG. 9 is a sectional view of the second embodiment of the present invention taken along line IXIX of FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings in greater detail, FIG. 1 shows a safety press 12 designed to prevent injury to operators thereof including a movable or traveling bolster assembly 10. The bolster assembly 10 is of the type disclosed and claimed in the parent of this application mentioned above, Ser. No. 263,147 entitled SAFETY APPARATUS FOR PRESSES, which application is incorporated by reference herein. The assembly may be used with all types of power presses of which the illustrated example is but one type. Specifically, the typical press 12 will include a frame 14, an upper movable ram or head 16, a lower press bed 18, and power means including a crankshaft (not shown) for reciprocating the ram 16 toward and away from the lower press bed 18. The bolster assembly 10 is fitted generally between the lower press bed 18 and the upper movable ram 16, and includes a traveling bolster plate 20 which supports and transports the lower portion of a punch-die combination, i.e., a die shoe 22 and a drawing die 24.

Bolster plate 20 is moved between a loading position 26 and working position 30. The loading position 26 is spaced a horizontal distance in front of the pinch area of the ram 16 and located such that the operator can reach the controls 28 for the bolster located above and in front of the ram area but cannot reach under the ram. In working position 30, the bolster 20, die shoe 22, and drawing die 24 are in alignment with the ram 16. Hydraulic or compressed air fluid cylinders (not shown) located generally in housings 32 and 34 provide motive power for movement of the bolster 20. The bolster moves on wheels or bearings over rails included in the housings.

A plurality of pressure pin-receiving holes or apertures 36 are provided at regular intervals through bolster plate 20, each of the holes receiving one generally cylindrical pressure pin 38. A draw ring 40 (FIG. 1) is typically mounted on the ends of the pins 38. Sheet metal or other material to be worked is laid over draw ring 40 which supports the material generally above drawing die 24. The material is securely clamped between ram 16 and draw ring 40 prior to the drawing or formation of the material over drawing die 24 as the ram is actuated downwardly through its working stroke. The downward movement of the pressure pins under the influence of the ram 16 is resisted by a buffer or fluid means such as an air cushion pad 42 (FIG. 2). The function of capturing and carrying pins 38 during the movement of the bolster 20 between the loading and working positions 26 and 30 and releasing the pins for the above-described reciprocal movement in the working position 30, is carried out by the apparatus of the present invention as is described hereinafter.

Referring now to FIGS. 2-4, a first embodiment of the pressure pin capturing and releasing apparatus of the present invention is shown generally at 50. Embodiment 50 includes a generally planar plate member 52 slidably mounted in a rectangular recess 54 formed in the bottom surface of bolster plate 20. Plate member 52 is mounted on longitudinally extending gib rails 56 on either lateral side thereof (FIGS. 3 and 4). As shown in FIG. 2, recess 54 is somewhat longer than the overall length of plate 52 in order to provide room for the plate to slidingly reciprocate therein. A plurality of pinreceiving apertures 58 are formed generally perpendicular to the plane of plate member 52 (FIG. 3) in positions which will correspond to the pinreceiving apertures 36 in bolster plate 20 when the two plates are aligned. Further, a like number of holes 62 corresponding to the number of holes 36 or 58 are formed extending generally perpendicularly through base plate I9 mounted over press bed 18 as shown in FIG. 2. Holes 62 receive cylindrical extensions 60 which are secured via appropriate securing means to air cushion 42 such that the pressure pins 38 will make contact with and be supported by extensions 60 when the pins are released in the working position.

Each of the pressure pins 38 received in holes 36, 58 is generally cylindrical and includes a large diameter portion 38a and a coaxial smaller diameter portion 38b (FIG. 7). A generally planar shoulder 44 extends between the larger and smaller diameter portions 38a and 38b, the shoulder including an annular bevel 45. The end of the smaller diameter portions 38b is also beveled at 46 to prevent any obstruction of movement over the press bed.

As is the best seen in FIG. 3, each hole 58 in plate member 52 includes a larger diameter recess 64 formed in the top surface of plate 52 around hole 58. Holes 58 themselves include two portions, portions 58a having diameters slightly larger than the diameter of portions 38a of pins 38, while portions 58b have diameters slightly larger than the smallest diameter portions 38b of pins 38. Recesses 64 are circular in shape and receive camming plates (FIG. 5) each of which cams one pin 38 between its released and captured positions as will be explained more fully hereinafter.

Plate member 52 is reciprocated in recess 54 between the pin-capturing and pin-releasing positions by arms 66 secured to the front of the plane member. Arms 66 extend through channels 68 which are rectangular in cross section, communicate with recess 54, and extend to the front of bolster plate 20. Depending downwardly from the forward end of each arm 66 is an extension 70, which extensions abut the front surface of press bed 18 as the bolster is moved into its working position as shown in FIG. 2. Until extensions 70 contact the front of the press bed, plate 52 is held in its capturing position, i.e., against the rear of recess 54 in bolster 20, by three spring arms 72 extending through holes 74 bored generally perpendicularly to the front edge surface of plate 52 through the bolster (see FIGS. 3 and 4). Spring arms 72 and plate 52 are biased by coil springs 76 held within hole 74 by threaded plugs 78. When extensions 70 abut against the front of bed 18, the continued movement of bolster plate 20 into its working position causes the bolster to slide over the top surface of the plate 52 bringing holes 36 into registry with holes 58b and 62 while simultaneously compressing the coil springs 76. Accordingly, it will be understood that the relative movement between plate 52 and bolster 20 is opposite one another as the holes are brought into registry.

Pins 38' are cammed between their release and captured positions by camming plates 80 received in the forward portion of recesses 64. The top surfaces of the camming plates are flush with the top surface of plate member 52 shown in FIGS. 2 and 7. As shown in FIGS. 5 and 6, each camming plate 80 comprises a generally semicircular plate having a rectilinear edge 82 and two countersunk, securing apertures 84. A recess 86 having an eccentric camming surface 88- is formed centrally in edge 82 to receive pins 38' in the captured position. Recess 86 is formed by boring a circular hole, having an interior surface 90, through plate 80 on a center located at A as shown in FIG. 5. Thereafter, hole 90 is eccentrically countersunk, beveled, or sloped on a center located at B. Center B is offset from the center at A such that the interior surface 90 and edge of the countersunk portions are exactly aligned at point C. Point C is equidistant from points D and D located at corresponding points on opposite sides of hole 90 on edge 82. Accordingly, as will be seen in FIG. 6, camming surface 88 slopes upwardly in two directions, namely, toward the top surface of camming plate 80 as well as toward point C. Therefore, pins 38 are easily and freely cammed by surface 88.

The actual camming of pins 38 between their captured and released positions is best understood from FIG. 7. When the bolster is under the ram, the pins are released and engage extensions 60 (shown in phantom). In this position, bevel 45 is generally horizontally aligned with camming surface 88. As the bolster is moved to its loading position (toward the left in FIG. 7), plate 52 remains stationary while bevel 45 engages surface 88 forcing pin 38 axially upward in hole 36. Plate 52 remains stationary until the rear of recess 54 engages the back of plate 52. At this point, pin 38 has been cammed away from and out of contact with extensions 60 such that shoulder 44 rests on the top surface of plate 80. The side of the smaller pin portion 38b abuts against the ends of holes 90 and 58b (shown in solid in FIG. 7). The pins rest securely and stably in this captured position and are therefore restrained from movement during the remaining movements of bolster 20 since the edge 82 of plate 80 extends into aperture 58 past the center line of the captured pin.

Pins 38 are released as bolster 20 is moved to its working position and plate 52 is simultaneously held motionless by the engagement of extensions on arms 66 with the front of the press bed. This inward movement of the bolster (toward the right in FIGS. 2 and 7) pushes pins 38 across the top surfaces of cam plate causing the pins to slide downwardly along camming surface 88 into their released position wherein they each engage an extension 60 from die cushion 42 (shown in phantom). In the released position, pins 38 are therefore completely free of camming plate 80 and may freely reciprocate under the opposing forces of the press ram 16 and die cushion 42.

ALTERNATIVE EMBODIMENT Another embodiment of the pin capturing and releasing system is shown in FIGS. 8 and 9 and differs primarily from the embodiment 50 in that no camming plates 80 are used in conjunction with the sliding plate member. As shown in FIGS. 8 and 9, the alternative embodiment 100 of the apparatus comprises a movable bolster 102 for supporting the drawing die 24 typically of the type shown in FIGS. I and 9. The drawing die has an upper portion comprising a punch 24a mounted on the upper movable ram 16 of the press 12 and a lower drawing die portion or drawing post 24b secured or fastened in place on the movable bolster 102'. At least one and usually a plurality of pressure pins 103 are reciprocally mounted in apertures 104- formed in the bolster 102. Apertures 104 extend through bolster 102 such that they are perpendicular to the supporting surface 106 of the bolster 102. Pins 103 support or draw ring or support 108. A buffer means or air cushion pad, similar to 42 above but without extensions 60, is provided in the power press 12 below the area in which the bolster 102 moves between its loading and working position such that the pad will engage the lower ends of the pressure pins 103 and resist their downward movement.

It will be understood that as the bolster 102 operates between its loading and working positions, a piece of material to be worked 110 will be positioned over draw post 24b in contact with draw ring 108. When the bolster is in its loading position, the work piece is positioned as shown in the left-hand portion of FIG. 9. The bolster is then moved to its working position where the punch 24a will be lowered such that the material 110 is clamped between the punch 24b and the draw ring 108. As the punch continues downwardly, the material 110 is forced downwardly over the draw post 24b thereby drawing the material into the desired shape. At the same time, the pressure pins 103 will be reciprocated downwardly against the resistance of the buffer means or air cushion pad 42 thereby securely maintaining the clamping of the material 110 during the drawing operation.

FIGS. 8 and 9 also illustrate how the second embodiment of the apparatus carries the pressure pins 103 during all movements of the traveling bolster 102' and allows the reciprocation of those pins only when the bolster is in its working position. As depicted therein, a clamping means 112 is provided in the bottom surface 114 of the movable bolster 102 in order to perform the above-described function. Clamping means 112 comprises a slidable plate member 116 mounted flush with the bottom surface 114 of the bolster 102 in a recess 118. The plate member 116 is held in place by two bar members 120 which are also flush with bottom surface 114 and extend along the length of the recess 118 provided for the plate member; Slots 122 are provided in the plate member 116 having different size.

ends 124 and 126 to alternately allow the reciprocation of the pressure pins 103 therethrough and to retain or clamp the pins in a raised position. The larger end 124 of slot 122 is formed to be slightly larger than the outside diameter of the main portion 105 of the pressure pins 103. The smaller end 126 of the slot 122 is formed slightly larger than the reduced diameter portion 107 of the lower end of the pressure pins 103. Themain portion 105 of the pressure pins is separated from the reduced diameter portion 107 thereof by a shoulder 109. Accordingly, when the pins 103 are in the raised position as shown in the left portion of FIG. 9. i.e., when the bolster 102 is traveling between the loading and working positions, the pins are captured and retained in the raised position by means of the smaller ends 126 of slots 122. However, when the bolster 102 is in the working position, the larger ends 124 of slots 122 are aligned with apertures 104 in bolster 102, and the pins 103 are allowed to reciprocate against the resistance of air cushion pad 42 by means of the force imposed by the ram or punch 24a.

Shifting or release means 128 are included to shift the sliding plate member 116 between the appropriate positions in order to allow the pressure pins 103 to reciprocate at the desired times. Shifting means 128 include biasing means such as springs 130 at one end of the sliding plate and block means such as stop blocks 132 at the opposite end of the sliding plate for correctly positioning the slidable plate member 116 at the proper time. Thus, as shown in FIG. 8, in the left-hand portion thereof, the bolster 102 is traveling toward the working position where it will be aligned with the upper movable ram 16 of power press 12. During such travel, the springs 130 continuously bias the plate member 116 toward its first clamping position wherein the smaller ends 126 of slots 122 engage shoulders 109 of the pins 103 thereby retaining those pins in their raised positions and causing them to move in unison with the traveling bolster 102. However, when the traveling bolster 102 reaches the working position beneath the upper movable ram, as shown in the right-hand portion of FIG. 11, the slidable plate member 116 is engaged by stop blocks 132 which are fixedly positioned in the working position of traveling bolster 102 on a portion of the power press 12. Consequently, stop blocks 132 contact one end of the slidable plate member 116, forcing it against the biasing force of springs 130 and moving it into its second or rlease position wherein the larger end 124 of slots 122 are aligned with the apertures 104 of bolster 102. Therefore, the bolster 102 and slidable plate member 116 will each be positioned in their respective second positions at the same time wherein the apertures 104 and larger ends 124 of slots 122 are aligned thereby allowing the reciprocation of pressure pins 103.

Accordingly, either of the embodiments 50 or 1.00 of the traveling bolster, incorporating the sliding plate members 52 or 116, respectively, allow the traveling bolster assembly to be incorporated on power presses of the type utilizing pressure pins and bumper means such as air cushion pads as described above. It will be understood that the slidable plate members are automatically shifted either by arms 66 or stopping blocks 128, between their two positions to allow the reciprocation of the pressure pins only when the traveling bolster is in its working position beneath the movable ram 16. At all other times, the sliding plate 52 with camming plate in embodiment 50 or the sliding plate 116 in embodiment secure and capture the pressure pins in a raised position thereby allowing the unhindered movement of the traveling bolster.

While several forms of the invention have been shown and described, other forms will now be apparent to those skilled in the art. Therefore, it will be understood that the embodiments shown in the drawings and described above are merely for illustrative purposes, and are not intended to limit the scope of the invention which is defined by the claims which follow.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows.

1. In a power press apparatus of the type including an upper-movable ram, a lower press bed, means for reciprocating said ram toward and away from said bed; a traveling bolster assembly for supporting and transporting a drawing die in repeated production usage; said apparatus including a bolster means movable between at least a loading position in which said bolster means and a drawing die supported thereby are displaced from alignment with said ram and wherein materials to be worked can be positioned with respect to said bolster means, and a working position in which said bolster means and supported drawing die are aligned with said ram and said material can be worked; said bolster means including pressure pin means and said press bed including die cushion means; said die cushion means biasing said pin means in a first direction generally toward said ram such that material to be worked is engaged by said pin means during the working of such material by said ram; the improvement comprising: restraining means on said bolster means for preventing said pressure pin means from reciprocating with respect to said bolster means at all times except when said bolster means is in said working position; said restraining means being mounted for movement in a second direction generally transverse to said first direction.

2. A power press apparatus as described in claim 1 wherein said bolster means comprises a bolster plate having a top surface, a bottom surface, a plurality of supporting wheels mounted thereon and at least one aperture bored perpendicularly with respect to said top surface through said bolster plate; said pressure pin means comprising at least one pressure pin reciprocally mounted within said aperture in said bolster plate; said restraining means comprising pin-engaging means for holding said pressure pin out of position for biasing action by said die cushion means so long as said bolster plate is not in said working position; and means for slidably-moving said pin-engaging means in a direction generally opposite the direction of movement of said bolster means to alternately release and capture said pin means.

3. The power press apparatus of claim 1 wherein said restraining means includes means for camming said pressure pin out of contact with said die cushion means as said bolster means reaches said workingposition.

4. Thepower press apparatus of claim 1 wherein said restraining means comprise a plate member mounted for movement on said bolster plate; said plate member including at least one aperture extending therethrough in said first direction; said bolster plate including at least one aperture extending therethrough also in said first direction for slidably receiving at least one of said pressure pins; a pressure pin mounted in said apertures; means for moving said plate member when said bolster plate reaches said working position whereby said apertures are brought into registry to allow said pressure pin to slide axially through both of said apertures.

5. The power press apparatus of claim 4 wherein said means for moving said plate member include biasing means biasing said plate member toward said working position and means for stopping said plate member before said bolster plate reaches said working position.

6. The power press apparatus of claim 4 wherein said plate member includes a top surface abutting said bolster plate and means for camming at least a portion of said pressure pin to said top surface to restrain said pin from axial movement in said apertures.

7. The power press apparatus of claim 5 wherein said bottom of said bolster plate includes a recess therein, said recess having a rear portion adjacent the rear of said bolster, said plate member being slidably disposed in said recess; said biasing means including a spring forcing said plate member toward said rear portion of said recess and said means for stopping said plate member comprising an arm extending forwardly of said plate member and having a downwardly depending stop for engaging the front of said press bed.

8. The power press apparatus of claim 6 wherein said camming means include a plate mounted in a recess in said top surface such that said plate is flush with said top surface; said plate having a portion extending into said aperture in said plate member, said extending portion including a recess extending to the edge of said aperture and having a camming surface inclined both upwardly to the top surface of said plate and toward a point on the inner edge of said recess, which point is equidistant from the edges of said extending portion on either side of said recess.

9. The power press of claim 6 wherein said pressure pin includes first and second coaxial, cylindrical portions with a shoulder surface therebetween extending generally perpendicular to said common axis; said first cylindrical portion having a diameter greater than said second portion; and an annular bevel between said first portion and said shoulder surface for engaging said camming means.

10. In a movable bolster assembly for presses, said assembly including means for movably mounting a bolster plate on a press having a reciprocal ram, a press bed and die cushion means for engaging and reciprocally moving pressure pins associated with a die mounted on said bolster plate, and means for moving said bolster plate between a loading position away from the working area of the ram and a working position beneath said ram; the improvement comprising: means for carrying at least one pressure pin mounted for reciprocal movement on said bolster plate during movement of said bolster plate between said loading and working positions; and means for releasing said pin and allowing it to reciprocate with respect to said bolster plate when said bolster plate reaches said working position; said releasing means being mounted for movement in a direction generally transverse to the direction in which said pin reciprocates.

11. The movable bolster assembly of claim 10 wherein said releasing means includes means for stopping its motion before said movable bolster reaches said working position whereby said pin is released.

12. The movable bolster assembly of claim 10 wherein said releasing means includes means for camming said pin away from the die cushion means on a press on which said bolster plate is mounted as said bolster plate is returned to its loading position.

13. The movable bolster assembly of claim 12 wherein said release means includes a plate member slidably mounted on said bolster plate; said plate member including said camming means thereon and means for moving said plate in a direction opposite the direction of motion of said bolster plate.

14. The movable bolster assembly of claim 13 wherein said plate member has front and rear portions, said plate moving means including an arm extending forwardly of said plate and having means depending from said arm for abutting the front of the press bed on which said assembly is mounted before said bolster plate reaches said working position.

15. The movable bolster assembly of claim 13 wherein said plate member and said bolster plate each include an aperture for receiving at least said one pressure pin; said plate moving means causing said apertures to be brought into alignment to allow said pin to reciprocate therethrough when said bolster plate is in said working position.

16. The movable bolster assembly of claim 13 wherein said camming means comprise a cam plate recessed in said plate member such that it is flush with the top surface thereof; said plate member being recessed in the bottom of said bolster plate; said plate member including an aperture extending therethrough generally perpendicular to the plane of said top surface thereof for receiving said pin; said cam plate extending into said aperture and having a camming surface for camming at least a portion of said pin to said top surface of said plate member.

17. The movable bolster assembly of claim 16 wherein said camming surface comprises a semicircular recess in the portion of said cam plate which extends into said aperture, said recess including an eccentric countersink forming a dual sloping camming surface.

18. A cam plate for alternately carrying and releasing pressure pins in a movable bolster assembly for presses, said cam plate including a generally planar portion having a free edge adapted to extend into an aperture which receives at least one pressure pin and a recess extending into said free edge; said recess including a camming surface for camming a pressure pin generally transverse to the general plane of said'planar portion.

19. The cam plate of claim 18 wherein said camming surface comprises an eccentric countersink on one edge of said recess.

20. The cam plate of claim 18 wherein said camming surface is a dual sloping surface whereby it slopes toward the surface of said generally planar portion as well as toward a point at the intersections of the edge of said recess and said surface of said generally planar por- 1 1 l2 tions, said point being equidistant from said free edge pressure pins in a movable bolster assembly for presses. adjacent either side of said recess. said cam plate including a recess, said recess having a 21. The cam plate of claim 18 wherein said recess is camming surface comprising an eccentric bevel on one semi-circular. edge of said recess.

22. A cam plate for alternately carrying and releasing 5 

1. In a power press apparatus of the type including an upper movable ram, a lower press bed, means for reciprocating said ram toward and away from said bed; a traveling bolster assembly for supporting and transporting a drawing die in repeated production usage; said apparatus including a bolster means movable between at least a loading position in which said bolster means and a drawing die supported thereby are displaced from alignment with said ram and wherein materials to be worked can be positioned with respect to said bolster means, and a working position in which said bolster means and supported drawing die are aligned with said ram and said material can be worked; said bolster means including pressure pin means and said press bed including die cushion means; said die cushion means biasing said pin means in a first direction generally toward said ram such that material to be worked is engaged by said pin means during the working of such material by said ram; the improvement comprising: restraining means on said bolster means for preventing said pressure pin means from reciprocating with respect to said bolster means at all times except when said bolster means is in said working position; said restraining means being mounted for movement in a second direction generally transverse to said first direction.
 2. A power press apparatus as described in Claim 1 wherein said bolster means comprises a bolster plate having a top surface, a bottom surface, a plurality of supporting wheels mounted thereon and at least one aperture bored perpendicularly with respect to said top surface through said bolster plate; said pressure pin means comprising at least one pressure pin reciprocally mounted within said aperture in said bolster plate; said restraining means comprising pin-engaging means for holding said pressure pin out of position for biasing action by said die cushion means so long as said bolster plate is not in said working position; and means for slidably moving said pin-engaging means in a direction generally opposite the direction of movement of said bolster means to alternately release and capture said pin means.
 3. The power press apparatus of claim 1 wherein said restraining means includes means for camming said pressure pin out of contact with said die cushion means as said bolster means reaches said working position.
 4. The power press apparatus of claim 1 wherein said restraining means comprise a plate member mounted for movement on said bolster plate; said plate member including at least one aperture extending therethrough in said first direction; said bolster plate including at least one aperture extending therethrough also in said first direction for slidably receiving at least one of said pressure pins; a pressure pin mounted in said apertures; means for moving said plate member when said bolster plate reaches said working position whereby said apertures are brought into registry to allow said pressure pin to slide axially through both of said apertures.
 5. The power press apparatus of claim 4 wherein said means for moving said plate member include biasing means biasing said plate member toward said working position and means for stopping said plate member before said bolster plate reaches said working position.
 6. The power press apparatus of claim 4 wherein said plate member includes a top surface abutting said bolster plate and means for camming at least a portion of said pressure pin to said top surface to restrain said pin from axial movement in said apertures.
 7. The power press apparatus of claim 5 wherein said bottom of said bolster plate includes a recess therein, said recess having a rear portion adjacent the rear of said bolster, said plate member being slidably disposed in said recess; said biasing means including a spring forcing said plate member toward said rear portion of said recess and said means for stopping said plate member comprising an arm extending forwardly of said plate member and having a downwardly depending stop for engaging the front of said press bed.
 8. The power press apparatus of claim 6 wherein said camming means include a plate mounted in a recess in said top surface such that said plate is flush with said top surface; said plate having a portion extending into said aperture in said plate member, said extending portion including a recess extending to the edge of said aperture and having a camming surface inclined both upwardly to the top surface of said plate and toward a point on the inner edge of said recess, which point is equidistant from the edges of said extending portion on either side of said recess.
 9. The power press of claim 6 wherein said pressure pin includes first and second coaxial, cylindrical portions with a shoulder surface therebetween extending generally perpendicular to said common axis; said first cylindrical portion having a diameter greater than said second portion; and an annular bevel between said first portion and said shoulder surface for engaging said camming means.
 10. In a movable bolster assembly for presses, said assembly including means for movably mounting a bolster plate on a press having a reciprocal ram, a press bed and die cushion means for engaging and reciprocally moving pressure pins associated with a die mounted on said bolster plate, and means for moving said bolster plate between a loading position away from the working area of the ram and a working position beneath said ram; the improvement comprising: means for carrying at least one pressure pin mounted for reciprocal movement on said bolster plate during movement of said bolster plate between said loading and working positions; and means for releasing said pin and allowing it to reciprocate with respect to said bolster plate when said bolster plate reaches said working position; said releasing means being mounted for movement in a direction generally transverse to the direction in which said pin reciprocates.
 11. The movable bolster assembly of claim 10 wherein said releasing means includes means for stopping its motion before said movable bolster reaches said working position whereby said pin is released.
 12. The movable bolster assembly of claim 10 wherein said releasing means includes means for camming said pin away from the die cushion means on a press on which said bolster plate is mounted as said bolster plate is returned to its loading position.
 13. The movable bolster assembly of claim 12 wherein said release means includes a plate member slidably mounted on said bolster plate; said plate member including said camming means thereon and means for moving said plate in a direction opposite the direction of motion of said bolster plate.
 14. The movable bolster assembly of claim 13 wherein said plate member has front and rear portions, said plate moving means including an arm extending forwardly of said plate and having means depending from said arm for abutting the front of the press bed on which said assembly is mounted before said bolster plate reaches said working position.
 15. The movable bolster assembly of claim 13 wherein said plate member and said bolster plate each include an aperture for receiving at least said one pressure pin; said plate moving means causing said apertures to be brought into alignment to allow said pin to reciprocate therethrough when said bolster plate is in said working position.
 16. The movable bolster assembly of claim 13 wherein said camming means comprise a cam plate recessed in said plate member such that it is flush with the top surface thereof; said plate member being recessed in the bottom of said bolster plate; said plate member including an aperture extending therethrough generally perpendicular to the plane of said top surface thereof for receiving said pin; said cam plate extending into said aperture and having a camming surface for camming at least a portion of said pin to said top surface of said plate member.
 17. The movable bolster assembly of claim 16 wherein said camming surface comprises a semi-circular recess in the portion of said cam plate which extends into said aperture, said recess including an eccentric countersink forming a dual sloping camming surface.
 18. A cam plate for alternately carrying and releasing pressure pins in a movable bolster assembly for presses, said cam plate including a generally planar portion having a free edge adapted to extend into an aperture which receives at least one pressure pin and a recess extending into said free edge; said recess including a camming surface for camming a pressure pin generally transverse to the general plane of said planar portion.
 19. The cam plate of claim 18 wherein said camming surface comprises an eccentric countersink on one edge of said recess.
 20. The cam plate of claim 18 wherein said camming surface is a dual sloping surface whereby it slopes toward the surface of said generally planar portion as well as toward a point at the intersections of the edge of said recess and said surface of said generally planar portions, said point being equidistant from said free edge adjacent either side of said recess.
 21. The cam plate of claim 18 wherein said recess is semi-circular.
 22. A cam plate for alternately carrying and releasing pressure pins in a movable bolster assembly for presses, said cam plate including a recess, said recess having a camming surface comprising an eccentrIc bevel on one edge of said recess. 